Such flow cytometric apparatus and methods are applicable in, among others, the fields of blood cell detection and particle analysis, for detecting or measuring the number and size of cells or particles.
In the fields of blood cell detection and particle analysis, the cells or particles to be detected generally flows through a small hole, and, by means of an optical or electrical detection procedure, the number and size information and the internal characteristics of the cells or particles can be obtained by analysis. In order that the cells or particles may pass through the small hole in a more regularly path, a clean liquid (sheath liquid) may be introduced to cover the sample which is under detection and passing through the small hole. In this way, the cells or particles can pass through the middle part of the small hole. As shown in FIG. 1, the sample particulates injected into a flow chamber 6 by a sample needle 7 are covered by the sheath liquid injected into the flow chamber 6 via a sheath liquid inlet 10, and pass through the small hole of the flow chamber 6 in a row in sequence, thus the detection can be conveniently performed. This process or method is referred as flow cytometry.
A general apparatus for carrying out flow cytometry is shown in FIG. 2, wherein reference numeral 5 represents a sample pool, the sample to be detected, which has been formed by reaction, being stored in the sample pool; reference numeral 12 represents a negative pressure pool which is connected with a negative pressure source 11 so that a negative pressure is maintained in the negative pressure pool 12 for drawing the sample from the sample pool 5 into a conveying line; reference numeral 13 represents a sheath liquid pool which is connected with a positive pressure source 14 so that a positive pressure is maintained in the sheath liquid pool 13 for providing the sheath liquid from the sheath liquid pool 13 to the flow chamber 6 under the driving power of the positive pressure provided from the sheath liquid pool 13; reference numeral 4 represents a sample injecting syringe, which provides a driving power to inject the sample into the flow chamber 6; reference numeral 6 represents a flow chamber, through which the sample to be detected is flowing and being detected at the meantime; reference numeral 7 represents a sample needle. the sample being injected into the flow chamber 6 through the sample needle 7; reference numeral 9 represents a waste pool, the sheath liquid and the sample, after passing through the small hole of the flow chamber 6, being discharged through a waste discharge port of the flow chamber to waste pool 9; reference numeral 17 represents a sample charging tube; and finally, reference numeral 3 represents a flow restrictor.
The process carried out by the above apparatus will be described now. First, a first normally-closed two-way valve V3 and a fourth normally-closed two-way valve V6 are opened, the sample prepared by reaction and brought into the sample pool 5 under the effect of the negative pressure of negative pressure pool 12 is drawn into a conveying line between the fourth two-way valve V6 and a storage tube 8 (which conveying line including the sample charging tube 17). Then the first two-way valve V3 and the fourth two-way valve V6 are closed, and a third normally-closed two-way valve V4 and a sixth normally-closed two-way valve V8 are opened, so that the sheath liquid flows through the flow chamber 6 under the effect of the positive pressure of the sheath liquid pool 13. Then the sample syringe 4 pushes the sample forward to feed it into the flow chamber 6. Alternatively, for feeding the sample to the flow chamber 6 more quickly, a fifth normally-closed two-way valve V7 may be opened in a short time period once, so that the sample is pushed forward quickly under the pressure provided by the sheath liquid pool 13. After the flow of the sample comes to a stable state, the detection to it can be initiated.
In the prior art described above, constant pressure sources provide the driving power for driving the sheath liquid and for charging the sample. The constant pressure sources are expensive for comprising two sets of air pressure sources and two sets of pressure regulators. Meanwhile, air conveying lines adopted in the apparatus result in an increased complexity of the system, which prevents the detection equipments adopting such apparatus from being miniaturized. In addition, a blockage in the flow chamber cannot be found out directly. Rather, the blockage in the flow chamber can be found out indirectly by an abnormal detection result. Thus, there is a certain possibility of making misjudgments, and it may be difficult to determine the location of the blockage. In the condition that the driving system with constant pressure sources is substituted by a driving system with a constant flow syringe, when the flow chamber is blocked, the pressure in the liquid conveying system will be increased dramatically. It follows that the fittings of the liquid conveying system disengage in a short time, and biologically dangerous liquid may be splashed out.